The Section on Molecular Neuroscience studies the molecular mechanisms of chemically coded ionotropic and metabotropic neurotransmission in the nervous system. The ultimate goals of the project are identifying molecular components of synaptic transmission, and how these components are regulated to allow short-term and long-term information to be encoded within postsynaptic neurons and neuroendocrine cells. With regard to slow transmission by neuropeptides, we believe that neuropeptides may occupy a special evolutionary niche for nervous system adaptation to paraphysiologicalIy stressors, and that by studying their roles in stress physiology, we might uncover roles (and treatments) relevant to human disease. In 2003-2004, we zeroed in on the role of the neuropeptide PACAP as a emergency response peptide in stress-mediated neuronal plasticity in the adrenal gland, in circadian adaptation to extremes of light and dark, and in neuroprotection following stroke. 1. The novel calcium-initiated signaling pathway propagated through calcineurin and CREB and regulating neuropeptide gene expression in bovine chromaffin cells (S. H. Hahm et al., Mol. Pharmacol., 64:1503-1511, 2003) is now being studied with respect to calcium-dependent regulation of PACAP signaling to the VIP gene and other genes involved in post-synaptic (cellular) plasticity mediated by PACAP at the adrenomedullary synapse (C. Hamelink et al., J. Neurochem. 88, 1091, 2004). A novel calcium-response element on the VIP gene has been identified that mediates PACAP- and depolarization-induced up-regulation of this gene (C. Hamelink and L. Eiden, in preparation, 2004). 2. The microarray tool mAdb has been refined for use by NIMH and extramural investigators and is being applied to the identification of a set of PACAP response transcripts (genes), neuroprotection transcripts (genes), and the overlap of these two sets in stroke (Y. Chen et al., in preparation, 2004), stress (see C. Hamelink, E. Weihe and L. E. Eiden, Pituitary Adenylate Cyclase-Activating Polypeptide, ed. by H. Vaudry and A. Arimura, 2003, chapter 10), and circadian function (M. Gillette, and P. Lindberg with SMN, in progress; G. Pickard with SMN, in progress). 3. A set of cyclic AMP-dependent transcripts (genes) has been identified in neuroendocrine cells that are regulated independently of protein kinase A and may represent a novel neuropeptide-stimulated gene ensemble (Grumolato et al., Endocrinol. 144, 2368, 2003; D. Vaudry et al, in preparation, 2004). In summary, the work of the Section on Molecular Neuroscience to identify the chemical neuroanatomy, signaling mechanisms and gene targets for slow transmission by PACAP in the nervous system has advanced through the identification of specific novel calcium- and cyclic AMP-dependent signaling pathways, cis-active elements on PACAP-responsive genes, and paraphysiological events in which PACAP signaling is required, including neuroprotective responses in stroke, glucohomeostatic responses in hypoglycemic shock, and circadian periodicity adjustment to extreme changes in, or disruption of, photoperiod. We expect to consolidate these findings and identify components of PACAP-specific neurotransmission underlying its role as an emergency response peptide in the coming year.